Sleep, it may seem, runs counter to our mobility. When we sleep, our limbs are dormant and we can’t seem to do anything; we can’t write, we can’t talk business, we can’t produce anything. Hasn’t someone said, “I’ve traveled a lot in my sleep, but I’m still in bed”? However, no one realizes that sleeping – a skill we have mastered since birth – seems to have become more and more problematic in recent years. Some people have insomnia all night, some people have difficulty falling asleep, some people struggle between sleep and wake up every day, either by the alarm wake up feeling not enough sleep, or really sleep to wake up naturally and then for the sleep time “too long” and feel guilty. In July, The New Yorker analyzed a series of studies on sleep in recent years and interviewed researchers to answer questions about why we have trouble falling asleep, what the benefits of sleep are, and what the effects of sleep deprivation are. Mr. Sai is here to provide a comprehensive report in the hope that readers will learn more about this process that we repeat every day. First, what affects our sleep? How do people fall asleep? Imagine the process. Your body temperature starts to drop and your hands and feet stay warm. Melatonin production increases, your brain gets the message that it needs to rest, your blood pressure drops, your heart rate slows, and your breathing calms. Then you gently fall asleep. Perfect! You can’t help but marvel. Don’t rush to praise just yet. In reality, that’s an idealized description. Sleep is not a simple process, and it seems to have become troublesome in recent years. Research and development by Charles Czeisler, director of sleep medicine at Brigham and Women’s Hospital (BWH), has found that the average amount of sleep people get on a weekday has dropped from eight and a half hours to less than seven over the past 50 years. In more detail, 31 percent of people are getting less than six hours of sleep a night, and 69 percent consider themselves sleep deprived. The decline in sleep isn’t just happening in the adult world, though – we humans as a species are all sleeping less than we used to. Dr. Lisa Matricciani, a sleep expert at the University of South Australia, analyzed data on children’s sleep from 1905 to 2008. She found that during this period, children’s sleep decreased by almost one minute per year. Basically, the problem with less sleep isn’t that we wake up earlier; most of the time it has a lot to do with when and how we choose to go to bed.Elizabeth Klerman is responsible for data analysis and modeling in the Department of Sleep Medicine at Brigham and Women’s Hospital. She studies how individual differences in our environment affect our circadian rhythm (circadian rhythm) and our ability to fall asleep. “No matter how tired you are, when you go to bed affects how long you sleep,” she says. How long it takes to fall asleep is influenced by a range of factors. To figure out the importance of each of these factors, Klerman first assessed the subjects’ habits, including when they usually went to sleep, when they woke up, and whether or not they used sleep-aiding medications because of problems they encountered during sleep. Once this information was gathered, Klerman and colleagues brought the subjects to the lab and monitored their sleep, assessing the impact of each factor on falling asleep. Genetic factors partially influence our sleep. Many sleep disorders, including insomnia and circadian rhythm disorders, are heavily influenced by genetic factors. If you don’t rest according to your daily routine because of circadian insomnia, your melatonin levels will drop: the hormone that informs you that you should be sleeping is not secreted enough, or the corresponding receptor is missing. However, we don’t yet have a full understanding of how genes affect sleep in humans. Dragana Rogulja, a neurobiologist at Jefferson University in the United States, has been studying the Drosophila melanogaster sleep cycle for years. She notes that sleep genes are conserved in many species and that fruit flies share many similarities with humans, such as the fact that they have a similar genetic makeup to humans and, like humans, prefer to go to bed at a set time each day. her and her colleagues’ study, published June 29 in Current Biology, shows that a genetic variant called Taranis exists in fruit flies that sleep less than their peers. “There are still many unanswered questions about sleep, especially the protein mechanisms that initiate the process at the molecular level.” Assistant professor Kyunghee Koh, another author of the paper, said the study identified new molecular pathways and brain regions that can control how long people sleep. Even so, human genes have not changed drastically in the past 100 years. Genetic predisposition doesn’t explain why so many people have sleep problems. Many researchers have found that good sleep hygiene is essential. Good sleep hygiene can even overcome the effects of some genetic factors. On the flip side, the effects of poor sleep hygiene can be just as bad as the worst genetic disorders. Factors in sleep hygiene also include lifestyle habits. Nicotine, caffeine, and alcohol all have a negative impact on sleep, and the negative effects are especially true when used just before bedtime. By participating in exercise and eating on time, we fall asleep a little faster; by eating too late or too much, falling asleep becomes difficult. This effect is reciprocal. Sleep disorders are also linked to weight gain. If you go to bed with an empty stomach, sleepiness will likewise escape without a trace. In fact, any change in plans can affect sleep. Rosalind Picard, director of the Emotional Computing Research Group at the MIT Media Lab, found that sleep irregularity is one of the most important factors affecting an individual’s sleep quality. Going to bed at a regular time is healthier than staying up all night and then catching up the next day. Regular sleep is equally helpful in getting higher GPAs and having a good mood. Probably the most important factor in this item of sleep hygiene is still the effect of light. Over the past century, light has become very prevalent at night. In fact, specialized photoreceptor cells in the human eye respond to changes in darkness and light and are used only in regulating our circadian rhythms. These melanopsin receptors are directly connected to the part of the brain that regulates the body’s biological clock. They act even in the blind: blind people know how their bodies regulate the biological clock even though they are aware. Light helps the body perceive the future by telling us how our surroundings will change in the coming hours or days and how our bodies can prepare for it. Harvard neuroscientist Steven Lockley says, “Our clocks have evolved to predict tomorrow.” However, this natural prediction system is now becoming squared away. Humans are increasingly surrounded by short-wave or “blue” light, which our circadian system mistakes for daylight. Computers, televisions, cell phones, and e-readers all emit blue light; 90% of Americans use electronic devices that emit blue light. When we use devices that emit blue light, we are actually sending signals to our brains to delay sleep. “What are we doing to our twilight?” Charles Czeisler sighs. When dusk is gradually postponed because of all this false daylight, we feel the spurt of energy instead of the melatonin we should be secreting. Czeisler found that artificial light can reverse our biological clocks by four to six time zones. This depends on what we are exposed to. In a study published earlier this year in the Proceedings of the National Academy of Sciences (PNAS), Czeisler and his colleagues had subjects read paperbacks or e-books for four hours before bed, in groups of five nights. The results were pretty shocking. Compared to those who read paper books, the subjects who read e-books secreted less melatonin and were less likely to feel sleepy, the time it took to secrete melatonin was pushed back by an hour and a half, and the biological clock was altered. It took them longer to fall asleep. They are also less alert the next morning. However, this is not true only for prolonged exposure to blue wave light. lockley, conducting a sleep lab, found that subjects showed these changes even when exposed to short wave light for less than 12 minutes. Many people who are unable to sleep seek out sleep aid medications. Unfortunately, available medications may not be sufficient to alter the effects of too much stimulation. The sleep we get with medication is different from regular sleep and may not be as effective as we think. Matt Bianchi, head of the Sleep Information Laboratory and the Division of Sleep Medicine at Massachusetts General Hospital, says that people who use sleep-assisting medications only sleep an average of 30 to 40 minutes longer than those who don’t. Moreover, there are no drugs on the market that fully mimic the natural pathways of sleep. Instead, many drugs inhibit rapid eye rotation and slow-wave sleep, which, Bianchi writes, can “compromise the rehabilitative value of sleep. The use of some sleep aids also poses a risk of ectomorphic sleep. Ectopic sleep is the behavior of eating or leaving the room while a person is asleep, and waking up with no recollection of having done so. In general, it is not recommended to use these medications consistently for longer than a week. Of course, there are non-pharmacological ways to promote sleep, and Lockley and Czeisler have developed a light system to help people become drowsy when they should be. The system starts by emitting light at a wavelength that keeps us awake, and then gradually changes to a longer, “warmer” light that tells our bodies to get ready for sleep. The system has also been adopted by NASA and will be installed in October 2016 on the International Space Station. For consumers, most electronic devices can be fitted with blue light filters. There are also ways to approach the behavioral approach. Susan Redline, a sleep researcher at Harvard Medical School, recommends cognitive-behavioral therapy. She believes that other “consciousness-body therapies,” such as tai chi, yoga, and meditation, may also be effective, and Redline is developing a yoga intervention for low-income Boston residents with sleep problems. This work is informed by research on the role of yoga exercise in promoting sleep. The Brazilian therapy developed under the leadership of Pedro Hallal, a researcher at the Federal University of Pelotas in Brazil, which provides free public arena services in low-income areas, holds good promise for improving sleep. Improving insomnia also requires finding more solutions. On the one hand, our sleep problems are worsening, and on the other hand, we don’t have too many good programs to deal with this change. Second, why do we need sleep? Nearly one-third of life is spent sleeping. Why do we need to sleep? When we sleep, our body consciousness is very fragile. Moreover, we do nothing while we sleep, and ostensibly produce no benefit. 1719, Cotton Mather, in a sermon, called excessive sleep “sinful” and bemoaned the fact that we often sleep when we should be working. Benjamin Franklin famously quipped, “A man will sleep in his grave.” For a long time, sleep was considered a useless piece of work, and even scientists who studied it thought it was hilarious. Harvard sleep researcher Robert Stickgold remembers his former collaborator J. Allan Hobson joking that the only function of sleep was to cure sleepiness.In 2006, brain neuroscientist Marcos Frank, in a paper examining the functions of sleep, summarized the effect of sleep on human cognition as “weak or vague.” Over the past decade, and especially in the last year, the mystery of sleep is being gradually unraveled. Indeed, sleep is an important part of our lives. We need to close our eyes, do nothing, and go into a state of sleep. Observing abnormalities in sleep can help us understand why humans need sleep. People with rapid eye movement (REM) sleep behavior disorder engage in motor activity consistent with dreaming when they enter the REM sleep state.REM sleep behavior disorder is a precursor to neurodegenerativedisease. A sleep research center in Montreal found that more than half of the patients with REM sleep behavior disorder showed clinical signs of neurodegenerative disease 12 years after the onset of the disorder, such as pauses in breathing for a few seconds or even minutes during sleep. Trials have shown that REM sleep behavior disorder is associated with diabetes and cardiovascular disease and can lead to cognitive dysfunction. Approximately 10% of dysfunction during wakefulness is the result of chronic insomnia. Chronic insomnia leads to poor quality of life, bringing about depression and an increase in cardiovascular disease, hypertension, cognitive function and motor dysfunction. Sleep is needed for the body to repair and maintain cognitive function. At the same time, sleep may be beneficial in relieving vascular tone. The fact that insomnia is correlated with the presence of depression suggests that sleep may help in coping with emotional stress or other chaotic developments. In 2000, a study by Stickgold published in Nature showed that sleep and dreaming play an important role in memory consolidation. Subjects were asked to spend seven hours a day for three days playing a game. Some had never played the game before, others were light on the game. The third group of subjects were amnesiacs who had severe damage to the medial temporal lobe and hippocampus. In this case, they were unable to form new memory fragments. Each night, as the subjects slept, they were constantly awakened and asked to recall what they had dreamed. The results proved that they dreamed about this played game. Surprisingly, even amnesiacs dreamed about this game. When they woke up the next day, the subjects could no longer remember the game or the person who woke them up in the middle of the night, but the shapes they recalled fit well with the pattern constructions they had previously observed in the game. Since then, evidence on the correlation between memory and memory function has begun to emerge. In 2013, Stickgold published a review summarizing other researchers’ progress in this area. He argued that sleep is not only crucial for memory consolidation, but also an extraordinary selection mechanism. Sometimes we remember something simply because it was exciting or sad. Sometimes we struggle to recall every trivial detail in order to figure out why something is important.Sleep and dreaming, Stickgold says, help us sift through material and store what’s important, whether that content is the gist of a mass of information or a specific detail. “In dreams, we get just the fragments. When we wake up, we know all.” Jan Born, a neurobiologist at the University of Tübingen, and Ullrich Wagner, a neuroscientist at the University of Münster, have asked subjects to answer a relatively complex math problem. The problem had a relatively simple solution, and the answer came quickly by using an abstract concept. Of course, the subjects did not know this. A few found the answer at the beginning. 8 hours later, each subject redid the problem. During this time, some were allowed to sleep while others were not. The results showed that only a quarter of those who didn’t sleep came up with the answer quickly, while 60 percent of those who slept during the eight hours found shortcuts to solve the problem. In effect, when we sleep, our brains replay our experiences during the day, processing, learning, and sifting through that information. In a sense, the brain sleeps and thinks at the same time. Our physical health also seems to be closely linked to sleep. To test the interplay between the heart and sleep, physiologists put a group of physically fit male subjects with no history of heart disease in a sleep-deprived state. At various points in time, the scientists measured the health of these subjects’ blood vessels, checking their heart rate, blood pressure, and levels of proteins associated with heart disease. Within two days, almost every indicator rose in the subjects. In contrast, a study of sleep apnea found that treatment for apnea improved blood vessel function. Once patients were able to sleep, the strain on the heart was relieved. The importance of sleep to brain function may be even more critical. In addition to its ability to impact memory and problem-solving functions, sleep can help keep the brain sharp, young and healthy. Two years ago, Maiken Nedergaard, a neuroscientist at the University of Rochester, published the results of years of research into the role of sleep. She analyzed the brains of rats when they were awake and asleep and found that sleep is the brain’s maintenance system. During wakefulness, our activities build up rubble in the brain where toxins form, such as beta-amyloid (Aβ), the beta-amyloid peptide that leads to the development of Alzheimer’s disease, while a number of normally innocuous proteins undergo misfolding.Abnormalities in Aβ are a biomarker for the earliest stages of Alzheimer’s disease, and a large number of studies have demonstrated the importance of Aβ accumulation in the brain pathology changes of Alzheimer’s disease and in the cognitive impairment. When we sleep, the brain’s lymphoid system (glymphatic system) expands, pumping cerebrospinal fluid (CSF) through the brain’s tissues back to the brain to clean it of waste. The lymphoid system is the purification system that processes the waste products of the brain cells. This is a tribute to the lymphatic system (lymphatic system), which is responsible for the cleansing of waste products from the body. Neurodegenerative diseases arise when the brain does not get enough rest and toxins accumulate within the brain. One of the earliest signs of dementia is sleep disturbance, and some of the genes that control the length of time are also associated with Alzheimer’s disease. Sleep disruption is the same biological mechanism that produces neurodegenerative diseases. All research shows that our bodies are doing important work while we sleep. However, very few people get enough sleep. Some people never even realize what it is like to be fully awake. What is your state when you don’t get a good night’s rest? More and more researchers are beginning to study how chronic sleep shortages affect our lives. Third, what are the consequences of sleep deprivation? Did you sleep well last night? Do you feel like you are fully awake and are now the brightest, smartest and most capable you? Unfortunately, this can only be a daydream for most Americans. Josna Adusumilli, a Harvard neurologist and sleep medicine expert, told The New Yorker that most people are not in the most optimal state of functioning. Between 50 and 70 million Americans suffer from chronic sleep disorders, she said. Sleep shortages can have serious consequences. Sleep inertia (sleep inertia) is a state of waking up groggy and not awake enough. Virtually everyone suffers from sleep inertia. The duration of sleep inertia depends largely on the amount and quality of sleep we get. If you are well rested, sleep inertia dissipates quickly. However, if you are not well rested, it can last throughout the day, making you unhappy and even posing a danger. Many people have experienced the consequences of sleep deprivation. Judith Owens, director of the Children’s Sleep Center at Boston Children’s Hospital, studied the effects of school hours on the health of school-age children. Her conclusions are less optimistic. Eight hours of sleep a day is enough for most adults, but toddlers need about 13 hours of sleep, including daytime naps. Teenagers, on the other hand, need about 9 1/2 hours; and, moreover, they tend to be night owls, who, according to the ideal circadian rhythm, should be late to bed and late to rise. Beginning in the 1960s, school schedules began to move up, which had a serious impact on students’ health. “Not only did this cause a lack of sleep, but it disrupted circadian rhythms.” Owens said. “They have to wake up when their brains are still in deep sleep. Waking up a child at 6 a.m. is like waking up an adult at 3 p.m. at night.” The result was similar to a persistent jet lag response and was worsened by too much sleep on weekends. Decision-making functions and emotional responses become worse. The ability to make good decisions is compromised and children may become easily frustrated. In fact, the increase in Attention Deficit Hyperactivity Disorder (A.D.H.D.) diagnoses may be partly a result of a child’s sleep deprivation. Symptoms of sleep deprivation in children include hyperactivity and impaired comprehension of external stimuli, and Owens has encountered many such misdiagnoses in her practice. Sleep deprivation also has an impact on physical development. Children who fall below the standard sleep schedule are more likely to develop obesity. Even for a 6-month-old baby, the amount of sleep predicts the amount of weight gained three years later. On the other hand, schools with healthier class schedules have better attendance, test scores, GPAs, and health. One study showed that by interfering with delayed school hours, not only did academic performance improve, but accidents involving automobile collisions decreased by 70 percent, and the rate of reported depression dropped.Owens found that even with a half-hour delay, results still improved. She says, “School hours should be timed with students’ health and status in mind, not for adult convenience.” As we age, the quality of our sleep only gets worse.Adusumilli says that if a person sleeps six hours a night for 12 days in a row – the amount of time many Americans sleep each year – his cognitive and physical performance become almost as indistinguishable from a person who doesn’t close his eyes for 24 hours. Sleeping 4 hours a night for 6 days consistently has the same result. A person who stays awake 24 hours a day performs similarly to a person with a blood alcohol concentration of 0.1%. In other words, a “normal” level of sleep deprivation allows us to perform as if we were drunk. In the short term, sleep deprivation has a profound effect on our performance. The first is on sensory and motor skills. In a study of college basketball players, well-rested athletes performed better than those who went about their usual routine. Emotional control is also affected; the connection between the prefrontal cortex of the brain and the amygdala is weakened, and we become prone to impulsivity and depression. Our ability to think and make decisions also plummets, with poor performance in learning, memory, simple calculations and analytical reasoning. Accidents and errors occur at an increased rate. In a study of interns at Brigham and Women’s Hospital, interns who worked regular jobs made twice as many errors per night due to inattention compared to those who worked short, 16-hour shifts and were given breaks, a result that has been repeated many times. The health effects of sleep deprivation are even more long-term. We are more susceptible to metabolic and endocrine problems such as weight gain, which leads to an increased risk of diabetes and cardiovascular disease; decreased immune function, which leads to an increased risk of cancer; and accelerated cognitive deterioration, which leads to an increased risk of dementia. Even if you start getting more sleep now, it may be too late, because children’s brains are growing and changing so quickly that they are more susceptible to the effects of sleep deprivation than adults; effects that can last a lifetime, no matter what they get used to later in life. For adults, short-term sleep deprivation is something we can still recover from. David Dinges, a sleep researcher at the University of Pennsylvania, found in his study that after five nights of sleep deprivation, one night of good sleep can re-energize you. It’s the quality of sleep that you want to recover from if you really are chronically sleep deprived. It can take weeks, sometimes longer, for the body to function back up. Often we don’t have the luxury of enjoying ten hours of sleep a night, even if it’s for a week, it’s too much of a luxury. Ironically, many people don’t really want to get more sleep even if they could. We don’t realize that we deprive ourselves of sleep. Many people believe that we have no problem sleeping 5 to 6 hours a day. We honestly believe that we are already achieving full wakefulness, which is optimal for us. However, we know very little about how much sleep we actually need. Elizabeth Klerman, a sleep scientist at Brigham and Women’s Hospital, had people follow their own sleep schedule for two weeks in a study. They could choose how long they would be awake and how long they would sleep each day. Then they entered a sleep lab.Klerman was interested in two things: preparation time for falling asleep and sleep duration. On the second day, she found that the subjects averaged 12 and a half hours of sleep, even though they could have also slept 16 hours, suggesting that they all suffered from a sleep shortage. On the first day in the lab, when testing sleep readiness time, some fell asleep before the technicians left the lab. In other words, they were extremely drowsy. However, they themselves thought they were awake and in good shape. Each of us has our own chosen “discomfort level,” Klerman says, but that doesn’t mean we’re really doing well. Charles Czeisler found that we realize the impact of sleep deprivation on our performance in the first day or two. Then, we don’t perform at our best, and we never experience it again. “That’s a different you,” Czeisler says. In another experiment, Kalerman looked at what factors limited how long subjects slept. She was impressed with one subject because he came back after he could sleep normally. He said he wished to fill out the form again to reevaluate his brain’s sensitivity and performance. He said that after catching up on sleep he realized how bad he had been before and wished to lower the score he had previously hit. “He had forgotten what a warning felt like before,” Klerman said. At the time, he thought he was sober and capable. “Why do you wish your brain could monitor you?” Klerman asked. Current research on sleep gives us a better understanding of sleep. All of us want to be productive and efficient, but when we try to improve our performance by working longer hours, it doesn’t actually do any good. The less rest we get, the more we only lose, the less productive we become, the less observant you would have been, the less happy you even feel, and even the more likely you are to get sick. No one knows how much of our abilities and health we sacrifice in the process. People will just tell you that it’s okay to sleep five or six hours a day and you’ll still perform well. In reality, we completely underestimate the value of sleep, even though it may have a fundamental impact on present and future performance. Unlike most things, sleep needs to be done personally. There is no one in this world who can sleep in your place.